bbonenfant / dted Goto Github PK

I receive drastically different elevation values for the same location when using DTED levels 0, 1, and 2. An area that I know to be approximately 735m MSL reports the following:

~/Desktop/dted/w117$ dted n34.dt0 --location 34.353932 -116.295523
1035.0 meters
~/Desktop/dted/w117$ dted n34.dt1 --location 34.353932 -116.295523
2557.0 meters
~/Desktop/dted/w117$ dted n34.dt2 --location 34.353932 -116.295523
733.0 meters

In looking at the source code, I believe the calculations for the latitude and longitude indices in the DTED data are wrong:

I believe this:

        lat_interval, lon_interval = self.dsi.latitude_interval, self.dsi.longitude_interval
        latitude_index = round(
            (latlon.latitude - origin_latitude) * (latitude_count - 1) / lat_interval
        )
        longitude_index = round(
            (latlon.longitude - origin_longitude) * (longitude_count - 1) / lon_interval
        )

Should be this:

        latitude_index = round(
            (latlon.latitude - origin_latitude) * (latitude_count - 1) 
        )
        longitude_index = round(
            (latlon.longitude - origin_longitude) * (longitude_count - 1)
        )

Hello,

I am trying to use the Tile(dted_file) on SRTM 1arc DTED files.
The publicly available SRTM 1arc data is actually not 1arc by 1arc but 2arc by 1arc, as soon as you are working with areas above 50° Latitude.

This causes the Tile() method to fail with the error:
dted.errors.InvalidFileError: Checksum failed for data block

When I try to ignore the checksum with load_data(perform_checksum=False), it fails with the error:
dted.errors.InvalidFileError: All data blocks within a DTED file must begin with 170. Found: 1

Do I just have to do something differently or is this something you could fix?
It works great otherwise!

Thank you for the help.

I am getting an error when importing Tile from dted. I am using a fresh Conda environment but cannot seem to get around this error. I can see the Tile class in dted/dted/tile.py but the import does not work. Error shown below:

ImportError: cannot import name 'Tile' from partially initialized module 'dted' (most likely due to a circular import) (/<PATH TO FILE>/dted.py)

Python Version: Python 3.9.12

Thanks for your help in advance!

It'd be very useful to have a directory full of dted files, and be able to query the pool of tiles instead of checking each individual one. It could get fancy with loading tiles as needed, tracking frequency of use to free up older ones, etc.